Report use of nowdoc strings in PHP < 5.3

[MarkMaldaba]

PHP added support for nowdoc strings[1] in PHP 5.3, so a Sniff should be added to report an error if targeting earlier versions.

[1] http://php.net/manual/en/language.types.string.php#language.types.string.syntax.nowdoc

[MarkMaldaba]

Also, the use of heredoc quoted strings (e.g. <<<"EOF" instead of <<<EOF) also introduced in PHP 5.3 (the old heredoc style without quotes has been around since PHP 4, so doesn't need a check).

Perhaps this should be a separate ticket?

[jrfnl]

Also, the use of heredoc quoted strings (e.g. <<<"EOF" instead of <<<EOF) also introduced in PHP 5.3

FYI: I've got the code ready in the backwings to add sniffing for this to the library.